The present invention relates to a method of producing alkyl 3-hydroxy-4-(4-hydroxyphenoxy)pentanoates, compounds used as critical intermediates in the production of aryloxy phenoxy pentanoate herbicides.
Aryloxy phenoxy alkyl acids and esters are well known herbicides and have been found to be particularly useful as post-emergent herbicides when used against grassy-type weed pests. These aryloxy phenoxy herbicides can be made a number of different ways, however, the primary method described in the literature comprises initially reacting a pyridine-type compound with a hydroguinone, followed by completion of subsequent processing steps. This method is described in U.S. Pat. Nos. 4,152,328 and 4,216,007. A problem with this method is that the initial starting compound, the pyridine-type compound, is very expensive, and subsequent processing steps dilute the percentage of pyridine moiety ending up in the end product, thus increasing significantly the cost of the final product which is obtained.
Desirably, the pyridine moeity is added at the end of the process in order to maximize the percent yield, and minimize the expense of the pyridine-type compound.
The present invention is thus concerned with a method of producing intermediates for the aryloxy phenoxy-type herbicides which intermediates enable the pyridyl moiety to be added at the end of the entire process. Such intermediates are alkyl 3-hydroxy-4-(4-hydroxyphenoxy)pentanoates.